Corrosive environments have long presented problems in application, installation, and maintenance of electrical equipment. The causes of corrosion and the means taken to date to combat corrosive environments are briefly reviewed. The application of new technology in the glass-reinforced polyester plastics field is described as a solution to the problem of long-term protection of electrical equipment installed in aggressive environments. This new technology involves the use of chemical thickening of special polyester resins suitably formulated to provide high levels of structural strength and corrosion resistance both indoors and outdoors. Data are presented on the environmental resistance of the chemically thickened glass-reinforced polyester systems, and these are interpreted in terms of the diffusion of the environment into and out of the plastic. Examples are given of the application of chemically thickened glass-reinforced plastics in heavy duty industrial plugs and receptacles, industrial type light reflectors, and enclosures for electrical equipment. The degree of protection afforded by the chemically thickened glass-reinforced plastic is important in electrical installations in the petroleum, petrochemical, food, drug, fertilizer, and other process industries.